Selective metal removal process for metallized retro-reflective and holographic films and radio frequency devices made therewith

ABSTRACT

A method for selectively removing metal from a metallized substrate (e.g., a metallized polymer film) and the formation of devices thereby are provided. The method involves selectively exposing the metallized surface to a demetallizing (i.e., an oxidizing) chemical solution. The metallized layer can be selectively exposed to the demetallizing solution using a flexographic printing process wherein printing rollers are used to transfer the demetallizing solution to the metallized surface. An identification device including, for example, a holographic, retro-reflective, or other metallized material and a radio-frequency transponder are also provided. The radio-frequency transponder includes an RF chip and an antenna in electrical communication with the chip. The identification device including the holographic image allows both electronic identification through the reading of identification data stored in the chip and optical identification via the holographic image.

RELATED APPLICATION INFORMATION

This application is a continuation application of U.S. patentapplication Ser. No. 10/118,092 filed on Apr. 9, 2002 including thespecification, claims, drawings and summary. The disclosure of the abovepatent applications is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a process for selectivelyremoving metallic material from a metallized film and, in particular, tothe removal of metallic material from a metallized polymeric film usinga printing method such as flexographic printing. The film can be areflective film (e.g., a retro-reflective film) or a holographic filmthat can be used, for example, in an identification device comprising aradio frequency (RF) transponder.

BACKGROUND OF THE TECHNOLOGY

Retro-reflective materials can reflect and re-emit incident light in adirection that is parallel to that of the source of the incident light.In other words, retro-reflective materials reflect light directly backtoward the source of the light. Such materials and devices are widelyused in the areas of nighttime transportation and safety. For example,retro-reflective materials are used to identify highway lanes and roadsigns using the light emitted from vehicle headlights. Retro-reflectivematerials are also used for the production of car plates, decals anddistinctives for all kinds of vehicles and for truck containers,tractors and other applications. Retro-reflective materials have abright effect under direct light without disturbing human sight.

Holographic materials have also been used for identification purposes.Since holograms are all but impossible to counterfeit, they are beingincreasingly used on all types of identification, including driver'slicenses, credit cards, bus passes, etc., to increase security.

Both retro-reflective and holographic materials typically contain a veryhigh level of metal such as aluminum. Holograms, for example, aretypically stamped from metal foils. It is known that metal blocks thetransmission and reception of radio frequency (RF) signals because theRF signal is absorbed or distorted by the metal content in the material.As a result, the signal cannot be received by an antenna blocked bymetal. Such a blocked signal cannot be used, for example, to activate aconnected device. This same blocking effect can occur whether the deviceis positioned on top of or underneath the metallic material because thedistortion and absorption of the RF signal will be affected in eithercase. Thus, there is a problem in the prior art with regard to usingretro-reflective and holographic materials, as well as other materialscontaining metals, on the surface of devices for receiving RF signals.

It would be desirable to incorporate an RF transponder into anidentification device comprising a retro-reflective material, aholographic image, or other material containing a metal. The RFtransponder could be used for electronic identification.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, an identification deviceis provided that includes retro-reflective or holographic materials, orother materials containing metal, and a usable antenna for receivingradio frequency (RF) signals. The identification device comprises: abase layer; an RF transponder comprising a mounted RF chip and anantenna disposed on the base layer; and a metallized region. Themetallized region can comprise a holographic image or a retro-reflectivelayer. The antenna is in electrical communication with the chip.According to this aspect of the invention, the metallized region hasbeen selectively demetallized such that the RF transponder can transmitand receive information.

According to a second aspect of the invention, a method of forming apattern in a metallized layer is provided. The method comprises:transferring a metal etching solution to portions of an exposed surfaceof the metallized layer using a printing process; allowing the etchingsolution to react with the metallized layer to selectively demetallizethe surface; and washing the selectively demetallized surface.

According to a third aspect of the invention, a method of making anidentification device comprising a base layer and at least one metalregion disposed thereon is provided. The method comprises: selectivelydemetallizing a first metal region of the device; forming a holographicimage in the first metal region; forming an antenna on the base layer;and mounting an RF chip on the base layer in electrical communicationwith the antenna to form an RF transponder. According to this aspect ofthe invention, the selective demetallization of the first metal regionallows the RF transponder to transmit and receive information.

According to a fourth aspect of the invention, a method of making anidentification device comprising a base layer and a metallizedretro-reflective layer is provided. The method comprises: forming aselectively demetallized retro-reflective layer on the base layer;forming an antenna on the base layer; and mounting an RF chip on thebase layer in electrical communication with the antenna to form an RFtransponder. According to this aspect of the invention, the selectivedemetallization of the retro-reflective layer retains theretro-reflective properties of the retro-reflective layer while allowingthe RF transponder to transmit and receive information.

Additional advantages and novel features of the invention will be setforth in part in the description that follows, and in part will becomemore apparent to those skilled in the art upon examination of thefollowing or upon learning by practice of the invention.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be described with reference to the accompanyingfigures, wherein:

FIG. 1 is a lateral cross-sectional view of a metallized substratesuitable for making an identification device according to the invention;

FIG. 2 is a top view of an identification device according to theinvention comprising a holographic image and an antenna;

FIG. 3 is a bottom view of the identification unit shown in FIG. 2,showing a chip module mounted on the bottom surface of theidentification device;

FIG. 4 is a lateral cross-sectional view of a further embodiment of adevice according to the invention, comprising two metallized layersarranged one above the other;

FIG. 5 is a top view of a device according to the invention, wherein theantenna is in electrical communication with the holographic image;

FIG. 6 is a top view of a further embodiment of an identification deviceaccording to the invention, wherein the device has a selectivelydemetallized holographic image;

FIG. 7 illustrates a method of making identification devices from acontinuous strip of metallized material having multiple segments thatmay be separated from the strip to make individual identificationdevices, in accordance with embodiments of the invention;

FIG. 8 illustrates a method of selectively removing metal from ametallized substrate according to the invention;

FIG. 9 shows an apparatus that can be used for the continuous selectivedemetallization of a metallized film according to the invention;

FIG. 10 shows a method of making a license plate having aretro-reflective layer and an RF transponder according to the invention;

FIG. 11 shows a license plate according to the invention, comprising aretro-reflective layer and an RF transponder made by the methodillustrated in FIG. 10;

FIG. 12 shows a method of forming an inlaid antenna according to theinvention; and

FIG. 13 shows a method of forming an identification device according tothe invention comprising inlaying an antenna in the base layer andoverlying a selectively demetallized retro-reflective layer.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have discovered a method by which a radiofrequency (RF) device can be integrated into an identification devicecomprising a metallized reflective (e.g., a retro-reflective) orholographic material. In particular, the present inventors havediscovered that, by selectively removing metal from the metallizedlayer, the conductivity of the metallized layer can be broken and theeffect of absorption and distortion of the radio waves that an RF deviceuses as a power source can be reduced. In this manner, a radio frequencydevice can be incorporated into a retro-reflective or holographicmaterial, such as a license plate, a decal (e.g., for a car licenseplate) or an identification card.

According to the invention, a demetallizing solution, such as a solutionof sodium hydroxide (NaOH), can be used in place of ink in a printingprocess to selectively demetallize a metal layer. In particular, thedemetallizing solution can be poured into the stainless steel trays of aprinting apparatus. The demetallizing solution can then be applied tothe metallized surface using a printing process. For example, thesolution can be applied to a printing plate having a raised pattern. Theplate can then be contacted with the metallized surface such that thesolution on the raised areas is transferred to the metallized surface.The application of the demetallizing solution to the metallized surfacecan be controlled by the inking rollers of a printing apparatus (e.g.,by the pressure applied to the inking rollers).

According to a preferred embodiment of the invention, the demetallizingsolution is applied to the metallized layer using a flexographicprinting process. The flexographic printing process is a rotary in-lineprinting method that uses flexible resilient plates with raised imagesto apply inks to a substrate. According to a preferred embodiment of theinvention, the flexographic printing process can be performed usinglaser-engraved anilox rolls to allow for high resolutions.

By using a printing process, such as a flexographic printing process,the sodium hydroxide solution can be transferred to selective portionsof the metallized film. In this manner, metal can be selectively removedfrom those areas. According to the invention, the exposure time of themetallized layer to the sodium hydroxide solution can be controlled toensure that the resulting chemical reaction sufficiently removes metalfrom the desired areas.

According to the invention, after the demetallization process iscomplete, the selectively demetallized film can be transferred to awashing unit where any excess or remaining chemical solution can beremoved. According to a preferred embodiment of the invention, washingof the demetallized surface can be accomplished using fine sprinklers.

The metallized film, which has been moistened by the previous wash, canthen be subjected to a residue evaporation process. Residue evaporationcan be accomplished using a set of two rolls (e.g., one made of rubber,one made of steel), as well as by such processes as use of air-cleaningfilters, sponges and/or blown air. The residue evaporation process canbe used as a preparation step preliminary to a heat-driven drying stage.During the heat-driven drying stage, the heat can be generated, forexample, by electrical resistance.

The metal removal process according to the invention can be used toproduce a metallized material that is non-blocking to radio frequencytransmissions. Therefore, a radio frequency device can be incorporatedinto an identification device (e.g. a card or plate) having a metallized(i.e., a retro-reflective or holographic) layer. As a result of thedemetallization process, the radio-frequency device can transmit orreceive information while in close proximity to the metallized layer.Additionally, by using a selective demetallization process according tothe invention, the metallized film can be made translucent. Therefore, avisible seal can be incorporated beneath the metallized layer accordingto the invention.

Features of the present invention directed to a metal-removal processfor a metallized material (e.g., a metallized polymer film) will now bedescribed in greater detail. According to a preferred embodiment of theinvention, the method comprises subjecting the metallized material to aflexographic printing process, wherein the inks are replaced by a metaletching solution. According to a preferred embodiment of the invention,the metal etching solution is an oxidizing solution. For example, anoxidizing solution can be poured into the stainless steel ink trays of astandard flexographic printing station. The oxidizing solution accordingto the invention preferably comprises sodium hydroxide (NaOH), water(H₂O), and, optionally, ethylene-glycol. The ethylene glycol can be usedas a density-reduction agent.

According to a preferred embodiment of the invention, the oxidizingsolution can be transferred to the inking rollers through a secondroller (i.e., an “anilox” roller). The oxidizing solution can then betransferred to a third roller, which conveys the solution to themetallized surface.

The exposure time of the metallized surface to the demetallizingsolution can be controlled to ensure that the resulting chemicalreaction removes the metal properly from the desired areas.

As set forth above, the demetallizing solution according to theinvention can be an aqueous solution of sodium hydroxide (NaOH). WhenNaOH contacts the metallic surface, the metal is converted into ametallic oxide via an oxidative chemical reaction. To stop thisoxidative process, the metallized surface can be washed with water. Forexample, the metallized surface can be washed using fine sprinklers tocover the entire metallized surface to ensure the removal of any residueand/or excess of the demetallizing solution.

The present invention also relates to the manufacture of anidentification device created with a metallized material (e.g., aretro-reflective or holographic material), which device includes a chipand an antenna (i.e., a radio frequency device). According to apreferred embodiment of the invention, the antenna can be formed fromthe same metallized layer used to manufacture the reflective orholographic material. When the device is made with a holographic image,an identification device can be provided having a capability of bothelectronic identification (i.e., via the reading of data stored in thechip) and optical identification (i.e., using the holographic image).For example, the device can be configured as an identification card thatallows an electronic identification through the reading of data storedin the chip and the optical identification via a check of the hologramon the device.

For the holographic image on the identification device, metallic filmssuch as aluminum films can be used. The metallic films can be grouped onthe device to form the hologram using known techniques. For example, thehologram can be made using conventional techniques, such as forming thehologram by stamping a metal foil with a hologram plate made using anengraving process.

In the case of identification cards or identification stickers, whichcan allow the transmission of identification data stored in a chip to areading device, a grouping technique can be used involving coupling atransporting unit with a chip and an antenna. The antenna can be made byplacing a wire conductor on the device or by etching the antenna in themetallic film.

A purpose of the invention is therefore to provide an identificationdevice that allows both optical identification via a holographic imageon the device and electronic identification via an RF chip mounted onthe device. The metallized layer can be used to prepare both the antennafor the RF device as well as to prepare the optical image on the device.The fact that the antenna and the image can be made from the samemetallized layer represents an advantage since only a single metallizedlayer is required. As a result, the manufacturing process can besimplified and the cost of manufacturing the device can be reduced.

Additionally, the antenna and the image device can be formed on oppositesides of a substrate material. It may also be advantageous to build theantenna on the device in several parts (i.e., by making one part of theantenna on the same side as the image device and the other part of theantenna on the side opposite the optical image). In this case, a highpower antenna can be made on a relatively small identification device.

Depending specifically of the desired frequency of the oscillatingcircuit made by the chip and the antenna, the antenna may be produced asa coil or as a dipole. To influence the oscillating chip frequencybehavior, it may be advantageous to use the image material at leastpartially to make an electronic commutation element. For example, theimage material may be used for making a part of the antenna. This isparticularly advantageous when the antenna is made as an antenna coil.It is also possible to use the image material to make a capacitorelement. To prevent the creation of metallic layers that may negativelyaffect the antenna's electromagnetic field, it may be useful tosuperimpose the image structure with a superficial structure to separatethe metallic surface from the hologram support, thereby creatingelectrically isolated partial metallic layers.

Turning to the figures, FIG. 1 shows the side view of an identificationunit 10 according to the invention having a substrate or base layer 11which has a metallized film or foil 12 mounted on its upper surface 33.The lower surface 30 of the substrate 11 is also shown. As shown, themetallized film or foil 12 comprises a film 13 coated with a metalliclayer 14. The film 13 is preferably a dielectric film, such as a polymerfilm. Polyethylene terephthalate (PET) is a preferred material for thefilm. Other materials, however, can also be used for the film 13. Thesubstrate is also preferably a dielectric material. However, thesubstrate 11 can be made of material with either electrically conductiveor dielectric properties depending on the type of film 13 used. Forexample, if the film 13 is a dielectric material, such as a polymerfilm, the substrate 11 does not have to be a dielectric material.

The identification device 10 shown in FIG. 1 can be in the form of acard or an identification label. A label is typically more flexible thanan identification card. The rigidity of the identification device can bevaried by the choice of the material used for substrate 11 and by thethickness of substrate 11.

In addition, it should be noted that the identification device 10 shownin FIG. 1 does not necessarily represent the actual end product but can,in addition to the layers shown in FIG. 1, be provided with furtherlayers, particularly layers covering the top and the bottom. Further, ifthe identification unit is to be constructed as an identification label,the device can be provided with an adhesive surface such as a pressuresensitive adhesive surface.

FIG. 2 is a top view of an identification device 10 according to theinvention. As shown in FIG. 2, metallized layer 12 has been divided intotwo fields placed in adjacent position: a holographic image field 16 andan antenna field 17. In the holographic field 16, the metallic film 12forms a holographic image 18 that can be transferred to theidentification device in a known manner (e.g., by using a stampingprocess) to form a hologram 20.

As shown in FIG. 2, the antenna field 17 comprises an antenna coil 22created, for example, by using a chemical etching technique according tothe invention. The coil as shown is provided on each end with contactfields 23 and 24. Contact fields 23 and 24 are provided as throughcontacts that provide an electric connection with the bottom surface 30of the base layer 11, as shown in FIG. 3.

For the construction of the antenna coil 22 shown in FIG. 2, a corrosivematerial (i.e., an aqueous NaOH solution) can be printed onto themetallic layer 14 to selectively remove portions of the metallic layer18 from the metal foil 12, thereby leaving behind only the area definedas the antenna coil 22.

FIG. 3 shows the bottom view of the device of FIG. 2. As shown in FIG.3, the contact points 23, 24 of the antenna coil 22 are connected asthrough-contacts to a chip 31 on the bottom side 30 of the substrate 11which, as shown, is mounted in a chip module 32 to make electricalcontact between the antenna 22 and chip 31 easier.

The antenna coil 22 and the chip 31 of the identification device 10shown in FIGS. 1 to 3 forms a transponder unit 34 which enables, bymeans of a reader unit, contact-free access to the data on the chip 31for purposes of electronic identification. At the same time, thehologram 20 mounted on the upper side of the identification unit 10enables optical identification to be made.

FIG. 4 illustrates an identification device 40 having two substrates 41,42 lying on top of each other, each of which has a metallized foil 45,46 mounted on its upper surface 43, 44. The components are arranged insuch a way that metallized foil 45 is positioned between substrates 41and 42 and metallized foil 46 is situated on the upper surface 43 of themetallized layer 41 and forms at the same time the top layer of theidentification device 40. As shown in FIG. 4, each of the metal foils45, 46 comprises a film or foil layer 47 having a metallized surface 39.According to a preferred embodiment of the invention, the metal foils45, 46 comprise a polymer film having a metallized surface comprisingaluminum.

In the identification unit 40 shown in FIG. 4, the upper metal foil 46is structured or divided up in the same way as metal foil 12 of FIG. 2.That is to say, the identification device 40 is provided with both ahologram 20, for example, in a hologram area 16 as well as an antennacoil 22 in an antenna area 17. As shown, the metal foil 45 mounted onthe upper side 44 of substrate 42 and arranged between substrate 42 andsubstrate 41 is provided with a second antenna coil 49 which is inelectrical contact with a first antenna coil located on antenna area 17via through-contacts with contact points 23, 24. The second antenna coil49 is itself connected by through-contacts with contact points 50, 51which themselves are connected to a chip module 53, which is mounted ina recess 52 in the bottom of substrate 42. In this way, the antennacoils 22 and 49 each form a component of the complete antenna unit 54 ofidentification device 40.

FIG. 5 illustrates a top view of an identification device 55 comprisinga metal foil 56 on the upper side of a substrate, not shown. In asimilar manner to metal foils 12 and 46 of FIGS. 2 and 4, respectively,identification device 55 comprises, for example, a hologram orretro-reflective area 57, or other metallized substance, and an antennaarea 58. The antenna area 58 as shown in FIG. 5 comprises a singleantenna coil 59, which can be created in the manner previously describedby selectively etching a metal foil made up of a metallic layer 61deposited on a film or foil layer (not shown). As shown, the antennacoil 59 is provided with contact points 62, 63. Contact points 62, 63can be designed as through-contacts connected to contact areas of a chipmodule 64 mounted on the bottom side of the substrate.

In the hologram or other metallized area 57 of metal foil 56, a hologramor other image 65 is formed in the metallic layer in the mannerpreviously described. As shown in FIG. 5, however, the hologram or othermetal material 65 comprises two image sections 66, 67 which areelectrically isolated from each other and which form, when viewed, acomplex connected optical structure. The smaller image section 67, iselectrically isolated from the larger image section 66. As shown, thesmaller image section 67 comprises two metal surfaces which appeargenerally as two U-shaped islands. As shown in FIG. 5, each of thesemetal surfaces are connected with a contact area 62 or 63 and form thepanels 68, 69 of a capacitor unit 70.

FIG. 6 shows an identification device 71 comprising a metal film 72,similar to the metal films 12, 46, 56 shown in FIGS. 2, 4, and 5,respectively. As shown, the identification device 71 also comprises aholographic field 73, which could also or alternatively include othertypes of images, or for example, retro-reflective material, and anantenna field 74. In contrast to the metal film 12 shown in FIG. 2,however, the metal film 72 is a reticulated metallic coating havinglines or stripes of metallic material 75. As a result, the image isformed from non-metallic fields 76 alternating with metallic fields 77.Such a structure can be created using the same process as the antennacoil 22 using the previously described printing/chemical etchingprocedure. In particular, the continuous metal coating in theholographic field 73 can be reticulated by printing lines of a chemicaletchant on the continuous metal coating. As a result, a reticulatedholographic material (i.e., with alternating lines or stripes ofmetallic material removed) can be formed.

When FIGS. 2 and 6 are compared, it can be seen that the image contentsof the holographic material 78 of FIG. 6 and the holographic material 20of FIG. 2 are similar. However, the images have different resolutions.In particular, the image in FIG. 6 has a lower resolution due to thereticulated structure of holographic material 78. However, thereticulated structure of holographic material 78 reduces interferencewith RF energy such that an RF transponder can be mounted on theidentification device 71.

FIG. 7 illustrates a method of manufacturing a metal foil having aholographic or other metallized field and an antenna field, such as themetal foil 12 shown in FIG. 2. In particular, a metal foil strip 25 witha large number of foil segments 26 connected to each other in continuousorder is shown in FIG. 7. When the metal foil strip 25 is separatedlengthwise along the dotted severance lines 27, individual metal foilsections, such as metal foil 12 in FIG. 2, can be provided.

As shown in FIG. 7, the metal foil strip 25 comprises, in the runningdirection 28, a sequence of hologram or other metallized areas 16 andantenna areas 17, continuously following on from each other, which, asshown, are situated on the left and right sides of a central runningline 29. The arrangement of the hologram or other metallized areas 16and the antenna areas 17 in one long line following each other in therunning direction 28 enables the continuous production of holograms orother metallized materials 20 in the hologram or other metallized area16 and of antenna coils 22 in the antenna area 17 when the metal foilstrip 25 moves forward in the running direction 28. In addition, theforward movement of the metal foil strip 25 can be phased in such a waythat, at various stages (indicated in FIG. 7 as stages I, II and III),various operations can be performed on the foil. In particular, theantenna area 17 on the metal foil strip 25 can undergo printing with ametal etchant in stage 1. The remains of the corrosive material can bewashed away, while, at the same time, the oxidized areas of the metalliclayer 14 can be removed in stage II. Finally, the antenna area 17 of themetal foil strip 25 can be dried (stage III).

In conjunction with the production of the antenna coil 22 in the antennaarea 17 of the metal foil strip 25, the metallized layer in theholographic or other metallized field 16 can be selectively demetallizedas shown in FIG. 7. Further, the holographic or other metallizedmaterial 20 can be formed in the hologram or other area 16 of the metalfoil strip 25 (e.g., by means of a revolving press) after thedemetallization process.

In order to construct the identification device 10 shown in FIG. 2, themetal foil strip 25 having holograms or other metallized materials 20formed in the hologram or other metallized areas 16 and antenna coils 22formed in the antenna areas 17 can be positioned on a substrate, notshown, laminated (e.g., with an adhesive) and separated along theseverance lines 27 to provide individual identification devices, such asthe identification device 10 shown in FIG. 2.

A demetallizing process according to the invention will now be describedin more detail.

Once the areas to be demetallized have been determined (e.g., usinggraphical design) a rubber engraving (e.g., flexographic plate) can bemade to cover the printing roller that is going to be used to depositthe demetallizing solution (e.g., an aqueous solution of sodiumhydroxide) on the metallized surface of the film. The sodium hydroxidesolution can, for example, be placed in one of the printing stations ofa conventional flexographic printing apparatus. For example, thedemetallizing solution can be placed in a stainless steel tray typicallyused for holding ink. The demetallizing solution can then be applied tothe metallized surface by means of the printing roller such that thedemetallizing solution is selectively transferred to areas of themetallized surface which are going to be demetallized. The volume ofsodium hydroxide that is “printed” on the metallized film can becontrolled, as with printing using ink, by, for example, the structure(i.e., the resolution) of the printing roller (i.e., the anilox roller)and the inking rollers and by the pressure that is exerted on theprinting roller.

Although the demetallizing effect is practically immediate once thedemetallizing solution is applied to the metallized surface, it may bedesirable to allow the demetallizing solution to remain a certain amountof time in contact with the metallized surface so that the chemicalreaction is completed in those areas in contact with the solution.

To stop the oxidizing effect of the solution, the metallized surface canbe washed with water (preferably non-recycled). For example, themetallized surface (previously printed) can be passed through a washingarea where the residual sodium hydroxide and the oxidized metal (i.e.,aluminum oxide) can be removed. In a preferred embodiment, the waterwill wet the entire printed area of the metallized surface. For example,fine sprinklers can be used to cover the entire printed area. In orderto make the washing process more efficient and to completely remove theresiduals of the chemical process, washing may be repeated one or moretimes using fresh water each time.

Before the film enters the drying station, it may be desirable to removeexcess water from the metallized surface in order to facilitate theevaporation of and remaining residual water. In order to remove thewater, it is recommendable to use a pair of rollers (e.g., one of rubberand another metallic), air cleaners, sponges and/or air sprinklers.Finally the film is passed through the drying unit through for a heatdry (e.g., using electrical resistance heating) to completely remove thewater from the material.

As a complement to the method of selective demetallizing, it is possibleto include in the same line of production an overprinting process withink. In this manner, the effects of demetallizing and printing can beobtained on the same material.

Compared with solvent based inks, water based inks are very manageable,clean and highly resistant to ultraviolet (UV) light. For these reasons,water based inks are desirable. Nevertheless, because one of thesub-processes of the demetallizing process is washing, it is preferableto print with water based inks after the demetallizing and washing stepshave been completed.

In addition, if certain metallized areas are desired not to be printed,it is possible to use a transparent solvent based varnish for printprotecting the metallized film. After print protection, the metallizedlayer can be demetallized. In this manner, higher resolutions can beachieved. This technique can be used in high security applications toproduce microtext and/or very fine lines.

A demetallizing process for use with a metallized, such as aretro-reflective material, according to the invention is described belowin reference to FIG. 8. First, any liner or protective layer 81 presenton the metal layer 83 is removed to expose the metal. In FIG. 8, themetal layer 132 is shown disposed on a carrier or base layer 78. Thecarrier or base layer 78 can be polyvinyl chloride or polyethyleneterephthalate. The metal layer 132 is then selectively exposed 79 to thecorrosive action of a corrosive material, such as a sodium hydroxidesolution, using a flexographic, screen, offset or any other printingprocess to remove metal from the desired areas. This process isdescribed in detail in Mexican Patent Application Nos. 2001/010968 and2001/010969 as well as in German Patent Application No. 101 21 126.These applications are herein incorporated in their entirety byreference. Selective metal removal can be used to form an antenna forthe RF transponder.

As a second step, a fine line demetallizing process can be performedover the remaining metal surface using the same demetallizing process tobreak the conductivity of the metal layer and the absorption ordistortion of radio waves. This allows the RF energy to be captured bythe antenna of the radio frequency device. This process is preferablydone at a high resolution to maintain the retro-reflective (or, forexample, holographic) properties of the remaining metal layer while, atthe same time, interrupting the conductivity of the metal to allow RFreception and transmission.

According to a preferred embodiment of the invention, the metallizedlayer is demetallized in a square grid pattern comprising a first set ofparallel lines of demetallized material oriented at right angels to asecond set of parallel lines or demetallized material. According to afurther embodiment of the invention, the squares of metallized materialin the square grid pattern will have dimensions of 5 mm×5 mm or less,more preferably 3 mm×3 mm or less. It has been found that, when thesquares of metallized material have dimensions of about 5 mm or less,shielding (i.e., distorion and/or absorption) is reduced to about 5% orless and when the squares of metallized material have dimensions ofabout 3 mm or less, shielding (i.e., distorion and/or absorption) isreduced to about 1% or less.

Although a square grid demetallized pattern is preferred, other patternscan be employed according to the invention. When other patterns areemployed, it is preferred that the longest straight line that can bedrawn on any metallized area is about 5 mm or less, more preferablyabout 3 mm or less.

A schematic of an apparatus for selective demetallization of a roll ofmetallized material is shown in FIG. 9. As shown in FIG. 9, metallizedmaterial (e.g., retro-reflective material) from a roll 121 is unrolledand passed over a printing roller 123 where a chemical etchant (e.g.,NaOH) from reservoir 35 is applied in a desired pattern. The printedmetallized layer is then passed over a temperature application roller128 to a washing station 36. After washing, hot air from dryer 37 isdirected over the surface of the washed material. Afterward, theselectively demetallized material is optionally transferred to variousprinting stations 38, 120 so that designs can be overprinted thereon.After over-printing, the metallized material can be transferred to anadhesive application roller 122 and adhesively bonded to a carriermaterial or base layer material 124. The base layer material 124 canhave perforations (not shown) to allow for separation of individualidentification devices from the continuous length. After bonding to thebase layer, the material is shown wound onto a take-off roller 126.

After exposing the material to the demetallizing agent, thedemetallizing process can be terminated by washing the surface withwater and immediately drying. Afterward, a design can be over-printed onthe identification device using a fixed or variable printing process.

Once the metal is removed from an area of the device, it is possible tomount a radio frequency device in the demetallized area. Theradio-frequency device can be used as a label or as an identificationtag, such as a car license plate.

In one example application, labels according to the invention can, forexample, be used for all types of vehicle control. The labels can beprovided in auto-adhesive form for use with a car license plate, atractor platform or for container information, vehicle controlapplications, etc. The labels can be provided with read and writecapabilities and can include biometric data, such as fingerprints, irisrecognition data, facial recognition data, voice recognition data,picture data and traffic violation data for drivers.

Car license plates are typically made from metal, acrylic orpolycarbonate. Regardless of the material, the process of applying an RFdevice will usually be similar. This process is described below withreference to FIG. 10 for a metal license plate. First, an upper surface82 of a metal plate 80 is embossed to form a depressed region 84. Anisolation layer 86 (e.g., a ferrite composite layer) is then depositedin depressed region 84. A radio frequency device 88 is then mounted onthe isolation layer. In this manner, RF device 88 is able to transmitand receive information without interference from the metal plate 80.Afterward, the license plate can be laminated with, for example, aselectively demetallized retro-reflective material 90. According to apreferred embodiment of the invention, the region of theretro-reflective material 90 above the area 92 where the radio frequencydevice 88 is mounted will be free of metallized material. Further, therest of the retro-reflective material 90 is preferably selectivelydemetallized with a fine line demetallizing pattern 94 using ademetallizing process as described above to reduce interference.

The resulting license plate is shown in FIG. 11. As can be seen fromFIG. 11, the license plate 94 comprises an antenna region 96 and aretro-reflective region 98. The retro-reflective region is shownover-printed with a license plate number. As can be seen from FIG. 11,the retro-reflective material has been removed from the antenna region96. The antenna can be formed by selectively demetallizing a continuousmetal layer using a printing procedure as described above.

An alternative process of forming the antenna comprises producing a thinpolymer layer (e.g., polyvinyl chloride (PVC) or polyethyleneterephthalate) having an antenna (preferably a copper antenna) embeddedtherein. Structures of this type are commonly referred to as inlays. Amethod of manufacturing an inlaid antenna according to the invention isshown in FIG. 12. As shown in FIG. 12, a conductive wire 100 (preferablya copper wire) is unrolled from a spool 102 and embedded in the surfaceof a polymer sheet 104. As shown in FIG. 12, the conductive wire 100passes over a thermal ultrasound head 106 and under a bridge 108 beforebeing embedded in the polymer sheet 104 to form the antenna 110. Theinlaid antenna can be applied with an auto-adhesive or pressuresensitive adhesive to the base layer or substrate of the identificationdevice. The antenna should be applied in an area of the device that hasbeen demetallized to avoid contact with any metal in the identificationdevice.

An alternative way of obtaining a retro-reflective or other metallizedmaterial on a metal plate or sticker can be employed wherein the carrieror base layer is a polymer such as PVC or PET. In this embodiment, theantenna can be embedded directly in the carrier using ultrasonic energyas set forth above. The retro-reflective or other metallized layer canthen be applied onto the carrier. Portions of the retro-reflective orother metallized layer overlying the antenna should be demetallized toavoid any contact of the antenna with the metal content of theretro-reflective or other metallized material. A fine linedemetallization process can be used as describe above over the remainderof the retro-reflective or other metallized material to minimize RFdistortion or absorption that can interfere with the radio frequencydevice. Afterward, an acrylic or epoxy resin can be applied to transformthe identification device into a label.

FIG. 13 shows an identification device according to this embodiment ofthe invention wherein an inlaid antenna 110 is positioned on a carrierlayer (not shown) beneath a demetallized portion 112 of aretro-reflective or other metallized layer 114. Also as shown in FIG.13, a fine line demetallizing process has been used on the continuousmetal portion 116 of the retro-reflective layer 114 to reduceinterference and thereby ensure adequate performance of the radiofrequency transmitting 118 and receiving 119 functions. In this manner,the retro-reflective or other metallized material properties can beretained while allowing for the adequate transmission and reception ofRF energy.

These and other modifications and variations to the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention.Furthermore, those of ordinary skill in the art will appreciate that theforegoing description is by way of example only, and is not intended tolimit the invention.

1. An identification device, comprising: a base layer; a radio-frequency(RF) transponder comprising an RF chip and an antenna disposed on thebase layer, wherein the antenna is in electrical communication with thechip; and a metallized region; wherein the metallized region has beenselectively demetallized, such that the RF transponder is able totransmit and receive information.
 2. The device of claim 1, wherein themetallized region includes an image.
 3. The device of claim 2, whereinthe image is a holographic image.
 4. The device of claim 1, wherein themetallized region includes a retro-reflective layer.
 5. The device ofclaim 1, wherein the metallized region comprises a holographic image andwherein the holographic image and the antenna form a single metal layer.6. The device of claim 1, wherein the base layer has at least one side,and wherein the antenna and the metallized region are located on thesame side of the base layer.
 7. The device of claim 1, wherein the baselayer has at least a first side and a second side, the first side beingopposite the second side, and wherein the antenna and the metallizedregion are located on opposite sides of the base layer.
 8. The device ofclaim 1, wherein the base layer has at least a first side and a secondside, the first side being opposite the second side, and wherein a firstpart of the antenna and the metallized region are located on the firstside, and a second part of the antenna is located on the second side ofthe base layer, and wherein the first part of the antenna iselectrically connected to the second part of the antenna.
 9. The deviceof claim 1, wherein the device comprises an upper metal layer positionedabove the base layer and a lower metal layer positioned below the baselayer, wherein a first part of the antenna is formed on the upper metallayer and a second part of the antenna is formed on the lower metallayer, the device further comprising a through contact connecting thefirst part of the antenna to the second part of the antenna.
 10. Thedevice of claim 1, wherein the metallized region is in electricalcommunication with the antenna.
 11. The device of claim 10, wherein themetallized region comprises an electronic commutation element.
 12. Thedevice of claim 10, wherein the metallized region comprises a capacitor.13. The device of claim 1, wherein the metallized region comprises aplurality of electrically isolated holographic regions.
 14. The deviceof claim 1, wherein the base layer is an electrically conductive layer.15. The device of claim 14, wherein an isolation layer is formed on thebase layer.
 16. The device of claim 15, wherein the radio frequency (RF)chip is mounted on the isolation layer.
 17. The device of claim 15,wherein the base layer includes a depressed region, and wherein theisolation layer is formed in the depressed region.
 18. The device ofclaim 1, wherein the base layer has at least one side, and wherein theantenna and the metallized region are formed on the same side of thebase layer in discrete, non-overlapping areas.
 19. The device of claim1, wherein the antenna comprises a conductive wire inlaid in a polymerlayer.
 20. The device of claim 1, wherein the device is selected fromthe group consisting of a decal, a license plate, and an identificationcard.
 21. The device of claim 1, wherein the metallized region has beenselectively demetallized in a square grid pattern.
 22. The device ofclaim 21, wherein the squares in the square grid pattern have a lengthof about 5 mm or less.
 23. The device of claim 21, wherein the squaresin the square grid pattern have a length of about 3 mm or less.
 24. Amethod of forming a pattern in a metallized region, the methodcomprising: transferring a metal etching solution to portions of anexposed surface of the metallized region using a printing process;allowing the etching solution to react with the metallized region toselectively demetallize the surface; and washing the selectivelydemetallized surface.
 25. The method of claim 24, wherein the printingprocess is selected from the group consisting of a flexographic printingprocess, an offset printing process and a screen printing process. 26.The method of claim 24, wherein the metal etching solution is an aqueoussolution of sodium hydroxide.
 27. The method of claim 26, wherein themetal etching solution further comprises ethylene glycol.